Add tests for powershell -? parsing

And all other accepted forms.

test/powershell/CoreConsoleHost.Tests.ps1

@@ -0,0 +1,12 @@
+Describe "CoreConsoleHost unit tests" {
+    $powershell = Join-Path -Path $PsHome -ChildPath "powershell"
+
+    Context "Command-line parsing" {
+
+        foreach ($x in "--help", "-help", "-h", "-?", "--he", "-hel", "--HELP", "-hEl") {
+            It "Accepts '$x' as a parameter for help" {
+                & $powershell -noprofile $x | ?{ $_ -match "usage: powershell" } | Should Not BeNullOrEmpty
+            }
+        }
+    }
+}